The preparation of a drug formulation for injection often requires the user to mix a drug with a diluent immediately prior to injection. This mixing step is a requirement for drugs known to have a relatively short shelf life in solution. For example, a drug comprising microspheres generally requires mixing with a diluent before administration. The dry microspheres of the drug are initially contained in a sealed vial, and the diluent is transferred from a syringe to the vial via an adaptor, which acts as a coupler between the syringe and the vial. With the diluent and microspheres in the vial, the user is directed to shake the syringe/vial adaptor/vial assembly (e.g., for approximately thirty seconds) to resuspend the microspheres in the diluent. The drug formulation can then be collected by syringe in the assembly and administered subcutaneously via a needle injection.
The mixing step is a critical step in the drug preparation that can be difficult for some patients to execute properly or efficiently. Generally, the syringe, vial adaptor, and vial are individually sealed but packaged together in a kit. Once the patient puts the syringe/vial adaptor/vial assembly together, the components cannot be separated until the product is mixed. Removing any of the components from the assembly prior to shaking exposes the contents of the vial to the ambient surrounding. Additionally, the assembly process creates a permanent hole in the vial seal through which the contents can leak out. The sealed assembly can be difficult to handle, and the duration and vigorousness of the shaking required for mixing can be difficult for some patients, especially those with arthritis or limited mobility/strength in their hands and arms. Furthermore, because the vial in the assembly typically constitutes one or more effective doses of the drug, a vial mistakenly dropped or damaged during the mixing step can be very costly to the user.
A variety of mixing devices for drug/diluent formulations have been proposed to facilitate the mixing of a drug and diluent in a sealed, sterile environment. One type of device utilizes a dual-compartment syringe. One compartment of the syringe contains the diluent, and the other compartment contains the drug. The sidewall of the syringe contains a groove just forward of the stopper between the chambers. As a plunger is pushed through the syringe, the groove allows fluid to leak into the drug chamber. The drug and diluent are combined as the fluid from the diluent chamber enters the drug chamber, and then the injection is administered. The disadvantages of this method include use of a non-custom syringe and an often insufficient physical mixing of the drug and diluent.
Another device utilizes a “bottomless vial” concept for mixing drugs with diluents before administration. This concept requires the drug manufacturer to place a drug inside a bottomless vial. A second bottomless vial filled with a liquid diluent is connected adjacent to the bottomless vial containing the drug. By creating pressure in the liquid diluent vial with a plunger, the fluid is transferred into the drug vial. The plunger is then disconnected from the diluent vial and re-attached to the vial now containing drug and diluent. A needle is also attached to the drug/diluent vial and after mixing, an injection is administered. The disadvantages of this method include the use of non-custom vials, a possible exposure of the drug/diluent to the environment, and manipulation steps which may be burdensome to some users.